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Numerical modeling of the power losses in geared transmissions: Windage, churning and cavitation simulations with a new integrated approach that drastically reduces the computational effort
No full textEnergy savings and efficient design are the new global trends. Gears are the main components in many applications like vehicle transmissions, industrial gearboxes etc. and although they are already highly efficient, there is still margin for improvement. Depending on the sector of application, energy saving produces also additional benefits such as a reduction of the pollutant emission in the automotive branch or an increased reliability/power density in compact applications like the precision planetary gearboxes. To perform efficiency improvements it is important to be able to compare different design solutions. A lot of research was made on gears but still today accurate power loss models are not available. Recently, the adoption of numerical techniques has enabled the overcoming of this problem but with the drawback of very long computational times. Considering the importance of such topic for gearbox manufacturers, the authors have developed a specific power loss calculation-tool that enables a good prediction accuracy with reasonable computational efforts. The model was validated with experimental tests performed by FZG showing good agreement
ANALISI DEGLI EFFETTI DELLE APPROSSIMAZIONI DELLO SPETTRO REALE DI CARICO SUL DANNEGGIAMENTO DELLE SINGOLE DENTATURE
No full textCFD simulation of power losses and lubricant flows in gearboxes
No full textEnergy efficiency represents one of the most relevant drivers in many application fields, and power transmission and gears play a critical and fundamental role in many of them, contributing to improve the overall efficiency and to reduce energy consumption and emissions. In the design phase, the availability of tools able to reliably anticipate the losses of a gearbox can provide a relevant contribution to the aim of improving efficiency. The power losses of gearboxes are the sum of different contributions. For some of them, the available analytical models can provide acceptable information but they are not suitable for an accurate prediction of the load-independent losses that are generated by the interaction of the gears with the lubricant. Computer simulation, in particular the application of Computational Fluid Dynamics (CFD), represents an approach to overcome the problem of predicting load-independent power losses accurately. Moreover, it can provide a description of the lubricant flows inside the gearbox, describing the oil supply to the critical components of the transmission, thus assessing the effectiveness of the lubrication system with respect to reliability. Nevertheless, the application of CFD to gears is challenging due to the geometrical properties of the volume domain to be studied and its variation during the meshing cycle, with the consequent complexity of the volume mesh handling. Many approaches have been proposed to apply CFD to gearboxes, and they differ in the accuracy of the results and of the simulation time. The paper proposed by the authors, on the basis of a preliminary review of the different approaches, describes the application of CFD to gearboxes based on an original global-remeshing technique, which enables accurate predictions in relatively short simulation times, compatible with the industrial design practice. The method is validated with data obtained by means of experimental tests, both on laboratory back-toback test rigs and on industrial gearboxes, including planetary gearboxes, for which the load-independent power losses are particularly relevant. The results of the CFD simulation are in very good accordance with the tests, both for the amount of the losses and for the flow distribution, and they also provide a tool to understand the origin of the losses, including the effects of churning, windage, pocketing, and cavitation. The results of the practical application used for the validation are included and discussed in the paper
Windage, churning and pocketing power losses of gears: different modeling approaches for different goals
No full textEnergy efficiency represents one of the most relevant trends in many fields, including the sector of power transmissions and gears, which are involved whenever power has to transmitted and transformed. For instance, in the automotive industry, gearboxes can contribute to the overall efficiency of the system and promote lower fuel consumption and emissions, both allowing an optimization of the whole system and reducing their own power losses. In many circumstances a better efficiency corresponds to lower operating temperatures and to a higher reliability of the systems, which can be related to the final profit, like in industrial applications, or even to the success, like for instance in motorsport racing. Improving the efficiency is therefore a main issue also for the gearbox manufacturers, and the availability of methods and tools to forecast the behavior with respect to lubrication and power losses since the beginning of the design phase strongly contributes to the goal. In the years, many empirical models were derived from experimental tests and have represented the only available tool for such purpose, but today, thanks to the recent developments in the computer science, numerical approaches allow a more accurate modeling of the physics behind the power dissipation and also allow a description of the oil flow inside a gearbox, which is fundamental with respect to the reliability of the components of the transmission. Both approaches, either derived from experimental tests or based on numerical simulations, have advantages and drawbacks. For each single case and problem, depending on the specific condition, the most appropriate model is not always the same. In this paper a review of the different available tools is proposed, describing critically the properties of the single approaches in order to understand when each of them should be preferred. The review also includes the latest developments by the authors, which have not been previously published yet
a new methodology for the prediction of the no load losses of gears: CFD and experimental investigation of the efficiiency of a planetary gearbox
No full textAnalysis of power losses in an industrial planetary speed reducer: Measurements and computational fluid dynamics calculations
Full text linkNumerical modeling of the churning power losses in planetary gearboxes: An innovative partitioning-based meshing methodology for the application of a computational effort reduction strategy to complex gearbox configurations
Full text linkThanks to the recent developments in the computer science, simulations are becoming an increasingly widespread approach that can help the designers in the development of new products. In the specific field of gearboxes, simulations are used mainly for structural evaluations. However, while for the structural design beside the simulations, many analytical methods and international standard are available; for the prediction of the power losses and the efficiency of gears, neither accurate analytical methods nor automated simulation tools are available. The authors work on this topic since years and have developed new methodologies based on computational fluid dynamics. With respect to general purpose commercial software, these techniques allow a significant reduction of the computational effort and have the capability to take into account particular physical phenomena that occurs in gears, such as cavitation, and for which no information are available in literature. The purpose of this paper is to introduce a new automated mesh-partitioning strategy implemented to extend the applicability of the previously developed computational effort reduction method to complex gearboxes getting over the geometrical limitations adopted in the past. To show the capabilities of this new strategy, we simulated a planetary gearbox that represents at the same time one of the most complicated kinematic arrangements of gears and the configuration for which the numerical fluid dynamics simulation can give the major contribution both with planar simplified models as well as with complete 3D models
Analysis of the Oil Squeezing Power Losses of a Spur Gear Pair by Mean of CFD Simulations
No full textComputational and experimental analysis of the churning power losses in an industrial planetary speed reducer
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